Electromagnetic (EM) noise in the RF and microwave (MW) range has become a serious problem for hospital buildings, computer centers, and other buildings where sensitive equipment is used. Most of these places present special problems because they have windows and doorways that admit EM noise from the outside and from one room to another. EM noise has also prompted health concerns relating to exposure from computer screens and other visual display devices (see, for example, U.S. Pat. No. 4,412,255 to Bruce E. Kuhiman and Marc A. Kamerling entitled “Transparent Electromagnetic Shield and Method of Manufacturing,” which issued Oct. 25, 1983). With these problems and concerns, a need has emerged for new types of windows that can attenuate EM noise.
Conductive wire-mesh shields and glass panel shields with transparent metal coatings have been proposed as solutions to the noise problem for display devices. Wire-mesh shields may attenuate EM noise for monochrome display devices but can seriously degrade signal patterns and produce color shifts for dot matrix color displays. Glass panel shields are extremely costly and difficult to work with, and their panels tend to be thick and heavy. Other types of shields that attenuate RF radiation are described in the following patents.
U.S. Pat. No. 6,353,220 to D. R. Sar entitled “Shielding of Light Transmitter/Receiver Against High-Power Radio-Frequency Radiation”, which issued Mar. 4, 2002, describes a method and apparatus for shielding a light transmitter or receiver from high-powered RF radiation using a window that contains water or brine.
U.S. Pat. No. 4,910,090 to B. E. Kuhlman et al. entitled “EMI/RFI Shield for Visual Display Terminals,” which issued Mar. 20,1990, describes a shield for use with visual displays.
U.S. Pat. No. 4,978,812 to K. Akeyoshi et al. entitled “Electromagnetic Wave Shielding Transparent Body,” which issued Dec. 18, 1990, describes a shield having transparent conductive sheets.
There remains a need for transparent windows for visual display devices that attenuate RF radiation. There also remains a need for RF-attenuating windows for buildings.
Therefore, an object of the present invention is to provide a transparent RF attenuator.
Another object of the present invention is to provide a transparent, RF-attenuator for buildings and visual display devices.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.